α,ε-Hybrid Peptide Foldamers: Self-Assembly of Peptide with Trans Carbon-Carbon Double Bonds in the Backbone and Its Saturated Analogue

Chitosan-based packaging films with an integrated antimicrobial peptide: Characterization, in vitro release and application to fresh pork preservation

Chitosan (CS) films were developed incorporating peptide HX-12C. The films were studied to determine their microstructures, physical properties, release properties of peptide HX-12C and functional properties. The results indicated that there may be hydrogen bonding interactions between CS and peptide HX-12C, thereby creating a homogeneous internal microstructure and lower crystallinity (10.8-12.8 %). Compared with CS film, CS-HX-12C films displayed lower light transmission, MC (20.8-19.9 %), WVP (8.82-8.59 × 10^-11·g·m^-1·s^-1·Pa^-1), OTR (0.015-0.037 cc/(m².day)) and higher WS (15.7-32.4 %) values. Moreover, controlled-release experiments showed that pH, ionic strength and temperature could all significantly affect the release of peptide HX-12C from the films. Finally, the increase of pH value and TVC and lipid oxidation of fresh pork were delayed due to the treatment with CS-2%HX-12C film. However, incorporating peptide HX-12C into CS films did not improve the mechanical properties of the films and their effects against protein oxidation. Our results suggest that the CS-based antimicrobial packaging films integrated with peptide HX-12C exhibit the potential for fresh pork preservation.

Advances in hybrid peptide-based self-assembly systems and their applications

Self-assembly of peptides demonstrates a great potential for designing highly ordered, finely tailored supramolecular arrangements enriched with high specificity, improved efficacy and biological activity. Along with natural peptides, hybrid peptide systems composed of natural and chemically diverse unnatural amino acids have been used in various fields, including drug delivery, wound healing, potent inhibition of diseases, and prevention of biomaterial related diseases to name a few. In this review, we provide a brief outline of various methods that have been utilized for obtaining fascinating structures that create an avenue to reproduce a range of functions resulting from these folds. An overview of different self-assembled structures as well as their applications will also be provided. We believe that this review is very relevant to the current scenario and will cover conformations of hybrid peptides and resulting self-assemblies from the late 20^th century through 2022. This review aims to be a comprehensive and reliable account of the hybrid peptide-based self-assembly owing to its enormous influence in understanding and mimicking biological processes.

Exploring Helical Folding in Oligomers of Cyclopentane-Based ϵ-Amino Acids: A Computational Study

The conformational preferences of oligopeptides of an ϵ‐amino acid (2‐((1R,3S)‐3‐(aminomethyl)cyclopentyl)acetic acid, Amc₅a) with a cyclopentane substituent in the C^β−C^γ−C^δ sequence of the backbone were investigated using DFT methods in chloroform and water. The most preferred conformation of Amc₅a oligomers (dimer to hexamer) was the H₁₆ helical structure both in chloroform and water. Four residues were found to be sufficient to induce a substantial H₁₆ helix population in solution. The Amc₅a hexamer adopted a stable left‐handed (M)‐2.3₁₆ helical conformation with a rise of 4.8 Å per turn. The hexamer of Ampa (an analogue of Amc₅a with replacing cyclopentane by pyrrolidine) adopted the right‐handed mixed (P)‐2.9_18/16 helical conformation in chloroform and the (M)‐2.4₁₆ helical conformation in water. Therefore, hexamers of ϵ‐amino acid residues exhibited different preferences of helical structures depending on the substituents in peptide backbone and the solvent polarity as well as the chain length.

The Diverse World of Foldamers: Endless Possibilities of Self-Assembly

Different classes of foldamers, which are synthetic oligomers that adopt well-defined conformations in solution, have been the subject of extensive studies devoted to the elucidation of the forces driving their secondary structures and their potential as bioactive molecules. Regardless of the backbone type (peptidic or abiotic), the most important features of foldamers are the high stability, easy predictability and tunability of their folding, as well as the possibility to endow them with enhanced biological functions, with respect to their natural counterparts, by the correct choice of monomers. Foldamers have also recently started playing a starring role in the self-assembly of higher-order structures. In this review, selected articles will be analyzed to show the striking number of self-assemblies obtained for foldamers with different backbones, which will be analyzed in order of increasing complexity. Starting from the simplest self-associations in solution (e.g., dimers of β-strands or helices, bundles, interpenetrating double and multiple helices), the formation of monolayers, vesicles, fibers, and eventually nanostructured solid tridimensional morphologies will be subsequently described. The experimental techniques used in the structural investigation, and in the determination of the driving forces and mechanisms underlying the self-assemblies, will be systematically reported. Where applicable, examples of biomimetic self-assembled foldamers and their interactions with biological components will be described.

Conformational Heterogeneity and Self-Assembly of α,β,γ-Hybrid Peptides Containing Fenamic Acid: Multistimuli-Responsive Phase-Selective Gelation

The effect of fenamic acid-α-aminoisobutyric acid corner motif in α,β,γ-hybrid peptides has been reported. From X-ray single-crystal diffraction studies, it is observed that Phe-containing peptide 1 has an "S"-shaped conformation that is stabilized by two consecutive intramolecular N-H···N hydrogen bonds. However, the tyrosine analogue peptide 2 has an "S"-shaped conformation, which is stabilized by consecutive intramolecular six-member N-H···N and seven-member N-H···O hydrogen bonds. The asymmetric unit of peptide 3 containing m-aminobenzoic acid has two molecules which are stabilized by multiple intermolecular hydrogen-bonding interactions. There are also π-π stacking interactions between the aromatic rings of fenamic acid. The peptides 1 and 2 have a polydisperse microsphere morphology, but peptide 3 has an entangled fiber-like morphology. Peptides 1-3 do not form organogels. However, in the presence of water, the peptide 3 forms a phase-selective instant gel in xylene. The gel exhibits high stability and thermal reversibility. The phase-selective gel of peptide 3 is highly responsive to H₂SO₄.